Technical Abstract:
Wyoming big sagebrush (Artemisia tridentata Nutt. ssp. wyomingensis Beetle & Young)-dominated rangelands of western Wyoming are under increasing pressure to provide a diversity of ecosystem goods and services for the public. For example, management practices that alter vegetation structure and cover offer opportunities for enhanced wildlife habitat diversity. In August 2009, we sampled areas dominated by Wyoming big sagebrush in western Wyoming that were thinned in 1997 by mowing (Sandy 7-9 GR ecological site) or by a selective herbicide in 2002 (Loamy 10-14W ecological site), as well as control, non-treated areas for each ecological site. Six, 25 m line transects were randomly located at each site and canopy cover of live Wyoming big sagebrush and grasses was determined. A 2 m belt was surveyed along the entire 25 length of each transect and the number of live Wyoming big sagebrush plants determined for density estimates. For the Sandy ecological site, mowing increased canopy cover of grass (10.7% vs. 0.9%) and decreased canopy cover of big sagebrush (11.9% vs. 24.0%) compared to control areas, and did not alter big sagebrush density (1.1 vs. 1.2 live plants m-2). For the Loamy ecological site, thinning with a selective herbicide resulted in much higher grass canopy cover (20.4% vs. 5.6%) and lower big sagebrush canopy cover (4.0% vs. 27.2%), and reduced density of live big sagebrush plants (0.6 vs. 2.2 live plants m-2), compared to non-treated, control areas. Modification of vegetation structure and cover through the use of brush management practices at both the Sandy and Loamy ecological sites provide opportunities for land managers to increase heterogeneity of vegetation in big sagebrush-dominated rangelands to achieve multiple ecosystem goods and services.